1. Field of the Invention
The present invention relates to a temperature controller unit for regulating to the desired heating temperature a dental agar impression material to be filled in a container, which is to be injected into a region to be subjected to impression taking in the oral cavity in dentistry.
2. Prior Art
In dentistry, the dental agar impression material to be injected into a region for taking an intra-oral impression is filled in a container such as a syringe for dental impression materials that takes the form of a solid rod at normal temperature and assumes the form of an injector or a cylindrical cartridge for dental impression materials that is closed up at one end with a rubbery membrane capable of forming easily a discharge port and fitted at the other end with a movable sealing piece. The dental agar impression material is heated to a first heating temperature (usually around 100.degree. C.) through the container to put it into a complete sol state, and is then cooled down to and maintained at a second heating temperature (usually around 60.degree. C.) at which an impression is to be taken giving no discomfort to patients. As occasion demands, the container is removed. In general, when the container is a syringe for dental impression materials, it may be used as such, whereas when the container is a cartridge for dental impression materials, it is attached for use to a syringe for the extrusion of dental impression materials designed exclusively therefor.
One system for heating and cooling such dental agar impression materials (hereinafter called the temperature controller unit for dental agar impression materials) has used boiling water as a heating medium for applying heat to the container filled therein with a dental agar impression material. With this type of system including a boiling water tank, the container having a dental agar impression material filled therein is charged into boiling water stored in the tank to heat it to the first heating temperature and, thereafter, cool and maintain it to and at the second heating temperature.
Another system available in the art has used a metallic body as a heating medium. With this type of system, the container having a dental agar impression material filled therein is brought (at the cylinder portion where the container is a syringe for dental impression materials or at the cylindrical portion where the container is a cartridge for dental impression materials) in contact with the metallic body including a heating source to heat the impression material to the first heating temperature and, thereafter, cool and maintain it to and at the second heating temperature.
Of such conventional temperature controller systems for dental agar impression materials as mentioned above, a problem with the former type is that if the dental agar impression material is heated from normal temperature at which it is solid to the first heating temperature to put it in a sol state and, then, cooled down to the second heating temperature at which they remain in a sol state through spontaneous cooling, then increased length of time is required to cool it to the second heating temperature, since high specific heat of water makes it difficult for hot water stored in the tank to cool down. For that reason, it is proposed to decrease the length of cooling time by incorporating relatively cold water, etc. into boiling water or providing another hot water tank in which stored is hot water maintained at the second heating temperature to keep the dental agar impression material in a sol state separately from the aforesaid boiling water-storing tank and transferring to said hot water tank the container having the dental agar impression material filled therein. However, such means for reducing the length of cooling time needs extra working steps that are time-consuming, and to handle the container in boiling water leads to a danger of a burn, etc. Additionally, it is unsanitary to maintain the hot water in the hot water tank at the second heating temperature for an extended period of time, since fungi tend to propagate. Moreover, it is uneconomical to provide two hot water tanks.
The latter type of system may not be used for some containers, although depending upon their dimensions and shape, since the portion of its metallic body to contact the containers is prescribed in terms of dimensions and shape. When the syringe for dental impression materials is used with this type of system, only its cylinder section comes in contact with the heating medium therefor, whereas its piston section serves as a heat radiator because of being not heated. As a consequence, the portion of the dental agar impression material in contact with the piston decreases in temperature and so tends to gel.